Gas-Fired Heating Appliance Having a Flammable Vapor Sensor Control Device

ABSTRACT

A gas-fired heating appliance includes a burner, a gas valve module for supplying a fuel gas to the burner, a power module for applying a voltage to the gas valve module, and a flammable vapor sensor module for detecting a flammable vapor. The flammable vapor sensor module interrupts the voltage to the gas valve to shut off the gas valve and the burner when the flammable vapor module detects the presence or a predetermined concentration of flammable vapor. The voltage of the power module is applied to the gas valve module through the flammable vapor sensor module. The voltage to the gas valve module is interrupted if the flammable vapor sensor module is short-circuited. This arrangement is tamper-resistant to promote a safe operation of the gas-fired heating appliance.

FIELD

The present disclosure relates generally to gas-fired heating appliances and their controls, and more particularly to gas-fired heating appliance controls incorporating a flammable vapor sensor control device.

BACKGROUND

The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.

Residential and commercial gas-fired heating appliances, such as water heaters, typically comprise a main burner and a standing pilot burner disposed within a combustion chamber below a cylindrical water tank. The main and standing pilot burners are supplied with a fuel gas through a gas valve, and air through an air inlet screen. Such standing pilot water heaters vent the combustion air without the use of a fan, and operate independently of the electrical power within the building. While conventional water heater appliances of this type operate reliably and safely, there may exist the possibility that the burners could cause flammable vapors external to the appliance to be ignited. The resulting flame could potentially propagate out of the appliance into the ambient environment around the appliance.

Efforts to mitigate any potential hazard posed by the presence of flammable vapors in proximity to a gas burning appliance have been previously directed to a control circuit in connection with a sensor that responds to the presence of flammable vapors to effect a shut down of the burner (e.g., by closing the gas valve). In a known flammable vapor sensor control circuit, the sensor experiences a significant increase in electrical resistance when it is exposed to a concentration of flammable vapors meeting a predetermined threshold. In such an instance, the sensor element cuts off the electrical current to a solenoid-actuated gas valve to close the fuel gas supply to both the main burner and the standing pilot burner, thereby shutting off the burners. The control circuit can prevent further operation of the burners until service or replacement of the control circuit or sensor.

While replacement of the sensor is a routine procedure to restore operation of the burners, it is possible that an end user may short-circuit the flammable vapor sensor control circuit as a matter of convenience to restore operation of the gas-fired heating appliance. As such, the appliance would operate without the safeguard of the flammable vapor sensor control circuit, which is undesirable.

SUMMARY

Several embodiments of the present disclosure provide for a tamper-resistant flammable vapor sensor control device to promote the safe operation of a gas-fired heating appliance. In one form, a control device for a gas-fired heating appliance includes a gas valve module, a flammable vapor sensor module and a power module. The gas valve module includes a gas valve adapted to supply a fuel gas to the gas-fired heating appliance. The flammable vapor sensor module detects the presence of a flammable vapor in an operating environment of the appliance. The power module provides an input to the flammable vapor sensor module. The flammable vapor sensor module provides an output to the gas valve module to maintain the gas valve in an open state. The flammable vapor sensor module interrupts the output to the gas valve module when a predetermined concentration of a flammable vapor is detected.

In another form, a gas-fired heating appliance includes a fuel gas burner and a flammable vapor sensor control device. The flammable vapor sensor control includes a gas valve adapted to supply a fuel gas to the burner when in an open state, a flammable vapor sensor module for detecting the presence of a flammable vapor in an operating environment of the appliance and a power module. The flammable vapor sensor module provides an output to the gas valve module to maintain the gas valve in the open state. The power module provides an input to the flammable vapor sensor module. The flammable vapor sensor module interrupts the output to the gas valve module when the flammable vapor sensor module detects a predetermined concentration of the flammable vapor in the operating environment.

In yet another form, a flammable vapor sensor control system for a gas-fired heating appliance includes a power module, a flammable vapor sensor module and a gas valve module. The power module includes a thermocouple. The flammable vapor sensor module is operable to detect the presence of a predetermined concentration of a flammable vapor within an operating environment of the appliance. The gas valve module includes a solenoid-actuated gas valve adapted to supply a fuel gas to the gas-fired heating appliance when energized. The thermocouple generates an electrical potential, which is applied to the flammable vapor sensor module. The flammable vapor sensor module energizes the gas valve in a first condition when a predetermined concentration of the flammable vapor is not present in the operating environment of the appliance, and de-energizes the gas valve in a second condition when a predetermined concentration of the flammable vapor is present in the operating environment of the appliance.

Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.

FIG. 1 is a schematic illustration of a gas-fired heating appliance employing a flammable vapor sensor control device in accordance with the teachings of the present disclosure; and

FIG. 2 is a schematic diagram of a control device for a gas-fired heating appliance in accordance with the teachings of the present disclosure.

Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses.

Referring to FIGS. 1 and 2, an exemplary gas-fired heating appliance is illustrated and generally indicated by reference numeral 10. The exemplary gas-fired heating appliance 10 takes the form of a water heater and includes a cylindrical water tank 12 and a main burner and a standing pilot burner (collectively burner 14) disposed within a combustion chamber 16 at the bottom of the appliance 10 below the cylindrical water tank 12 in a well-known manner.

The gas-fired heating appliance 10 further includes a control device 20 for the gas-fired heating appliance 10. The control device 20 includes a power module 22, a flammable vapor sensor module 24 and a gas valve module 26. The power module 22 includes a thermocouple 28 disposed adjacent to a pilot flame and includes a pair of output terminals 30.

The gas valve module 26 includes a gas valve 32 for supplying a fuel gas to the appliance 10 and a solenoid 34 for energizing or de-energizing the gas valve 32. The gas valve module 26 controls the supply of a fuel gas through a supply line 36 to the burner 14. The control device 20 includes a knob 38 that must be depressed to supply the fuel gas while lighting a pilot burner flame.

The flammable vapor sensor module 24 is connected between the power module 22 and the gas valve module 26 for detecting the presence of a flammable vapor 40 in an operating environment of the appliance 10.

The flammable vapor sensor module 24 includes a chemiresistor sensor 42 for detecting the presence of flammable vapor 40. When the chemiresistor sensor 42 is exposed to flammable vapor 40, the resistance of the chemiresistor sensor 42 changes, indicating the presence of flammable vapor 40. Exemplary vapor sensor circuits and resistive vapor sensor elements are disclosed in U.S. Pat. No. 7,112,304, entitled “Robust Chemiresistor Sensor,” and U.S. patent application Ser. No. 11/286,985, filed Nov. 23, 2005, entitled “Temperature Compensated Vapor Sensor,” both assigned to the assignee of the present application, Therm-O-Disc, Incorporated, the contents of which are incorporated herein by reference in their entirety.

The thermocouple 28 is disposed adjacent to a pilot flame. When the thermocouple 28 is heated by the pilot flame, a voltage is created across the output terminals 30 of the thermocouple 28. The output terminals 30 of the thermocouple 28 are connected to the flammable vapor sensor module 24 so that the thermocouple 28 provides an input to the flammable vapor sensor module 24. The flammable vapor sensor module 24 may include a flammable vapor sensor circuit (not shown), which is connected in series or parallel with the power module 22. The flammable vapor sensor module 24 receives the voltage input from the power module 22 and applies a voltage output to the gas valve module 26. When the voltage is applied to the gas valve module 26, the gas valve 32 of the gas valve module 26 is energized to an open position and allows the fuel gas to flow from a gas source (not shown) to the heating appliance 10.

When the chemiresistor sensor 42 is exposed to flammable vapor, the resistance of the chemiresistor sensor 42 increases or decreases depending on the type of sensor and its application. As the resistance changes to a value corresponding to a threshold concentration of the flammable vapor 40, this changed resistance causes interruption of the power applied to the gas valve module 26, thereby de-energizing the gas valve 32, causing it to close and discontinue the flow of fuel gas to the burner 14. By discontinuing fuel gas to the burner 14, the burner 14 of the heating appliance 10 cannot serve as a possible ignition source for the flammable vapor 40. The operation of the gas-fired heating appliance 10 can be restored, for example, after the flammable vapor sensor module 24 is replaced or the control device 20 is otherwise serviced.

An exemplary operation of such flammable vapor sensor is disclosed in U.S. Pat. No. 7,112,059, entitled “Apparatus and Method for Shutting Down Fuel Fired Appliance”, the content of which is incorporated herein by reference in its entirety.

It should be appreciated that a vapor sensor control circuit assembly may be modified from that described, above, to accommodate a capacitive vapor sensor element such as that disclosed in U.S. patent application Ser. No. 11/297,752, filed Dec. 8, 2005 and entitled “Capacitive Vapor Sensor.” This patent application is assigned to the assignee of the present application, Therm-O-Disc, Incorporated. The contents of this application are incorporated herein by reference in their entirety.

Because the output terminals 30 of the thermocouple 28 are connected to the flammable vapor sensor module 24, an end user cannot easily circumvent the flammable vapor sensor module 24. If the end user attempts to short-circuit the flammable vapor sensor module 24, the output voltage of the thermocouple 28 cannot be applied to the gas valve module 26 and no fuel gas can be supplied to the burner 14 in the absence of the flammable vapor sensor module 24. Accordingly, the flammable vapor sensor control device 20 of the present disclosure resists tampering to promote a safe operation of a gas-fired heating appliance 10.

This description is merely exemplary in nature and, thus, variations that do not depart from the gist of the disclosure are intended to be within the scope of the disclosure. Such variations are not to be regarded as a departure from the spirit and scope of the invention. 

1. A control for a gas-fired heating appliance, comprising: a gas valve module comprising a gas valve adapted to supply a fuel gas to the gas-fired heating appliance; a flammable vapor sensor module for detecting the presence of a flammable vapor in an operating environment of the appliance; and a power module for providing an input to the flammable vapor sensor module, the flammable vapor sensor module providing an output to the gas valve module to maintain the gas valve in an open state; wherein the flammable vapor sensor module interrupts the output to the gas valve module when a predetermined concentration of the flammable vapor is detected.
 2. The control of claim 1, wherein the power module includes a thermocouple.
 3. The control of claim 1, wherein the flammable vapor sensor module includes a chemiresistor sensor, the resistance of which changes in the presence of the flammable vapor.
 4. The control of claim 1, wherein the gas valve module includes a solenoid.
 5. The control of claim 1, wherein the flammable vapor sensor module includes a flammable vapor sensor circuit connected in series with the power module.
 6. The control of claim 1, wherein the flammable vapor sensor module includes a flammable vapor sensor circuit connected in parallel with the power module.
 7. A gas-fired heating appliance, comprising: a fuel gas burner; and a flammable vapor sensor control comprising: a gas valve module including a gas valve adapted to supply a fuel gas to the burner when in an open state; a flammable vapor sensor module for detecting the presence of a flammable vapor in an operating environment of the appliance, the flammable vapor sensor module providing an output to the gas valve module to maintain the gas valve in the open state; and a power module providing an input to the flammable vapor sensor module; wherein the flammable vapor sensor module interrupts the output to the gas valve module when the flammable vapor sensor module detects a predetermined concentration of the flammable vapor in the operating environment.
 8. The gas-fired heating appliance of claim 7, wherein the power module includes a thermocouple.
 9. The gas-fired heating appliance of claim 8, wherein the thermocouple is heated by a pilot flame of the burner, the thermocouple generating an electrical potential when heated.
 10. The gas-fired heating appliance of claim 7, wherein the flammable vapor sensor module includes a chemiresistive sensor, the resistance of which changes in the presence of the flammable vapor.
 11. The gas-fired heating appliance of claim 7, wherein the gas valve module includes a solenoid energized by the output of the flammable vapor sensor module.
 12. A flammable vapor sensor control system for a gas-fired heating appliance, comprising: a power module comprising a thermocouple; a flammable vapor sensor module operable to detect the presence of a predetermined concentration of a flammable vapor within an operating environment of the appliance; and a gas valve module comprising a solenoid-actuated gas valve adapted to supply a fuel gas to the gas-fired heating appliance when energized, wherein the thermocouple generates an electrical potential, the electrical potential applied to the flammable vapor sensor module, the flammable vapor sensor module energizing the gas valve in a first condition when a predetermined concentration of the flammable vapor is not present in the operating environment of the appliance, and de-energizing the gas valve in a second condition when a predetermined concentration of the flammable vapor is present in the operating environment of the appliance.
 13. The flammable vapor sensor control system of claim 12, wherein the electric circuit of the flammable vapor sensor module comprises a chemiresistor sensor the resistance of which increases in the presence of flammable vapor. 